Method of making evacuated valves



Dec. 19, 1944. R DE Q MCD|LAL 2,365,285

METHOD 0F MAKING BVACATED VALVES Original Filed July 13, 1942 Patented Dec. 19, 1944 ,UNITE-D PATENT- OFFICE Rex De Ore McDill, Cleveland, Ohio, assignor to Thompson Products Incorporated, Cleveland, Ohio, a corporation of yOhio lOriginal application! July 13, `1942, Serial No.

450,685. Divided and this application April 19, v l1943, Serial No. 483,617

, 1, claim. (ci. 21a-156.7) .I

This invention relates to a method of vmaking I hollow evacuated poppetvalves or the like for use in internal combustion engines. f

More particularly the invention relates to a method of evacuating coolant-containing hollow Y such as me`' poppet valves by reacting coolants tallic sodium with oxygen. l

This application is a division of my ,application Serial 450,685, filed'July 13, 194.2.

It has heretofore been proposed to fabricate hollow valves partially filled with ajliquid or liquefable coolant having a vaporizing temperature greatly in excess of the usual operating temperature of the valves. Valves of this type are disclosed in the patents to Heron Nos. 1,670,965 and 1,823,452 as containing metallic sodium, vthe internal space above the sodium being filled with air. When such valves are operated, the temperature rises from the relatively cold starting temperature and the sodium is gradually. melted but is not vaporized due to the high internalI pressure Within the valve.l The liquefied sodium functions as a coolant by being heated in the valve head cavity and, on being bodily transferred to the valve stem when the valve reciprocates, delivering the heat picked up in the'valve head to the valve stem whence the heat is dissipated. v

It is highly desirable to conduct" heat away from the valve head as rapidly as possible, be-

are heated,the oxygenv Acombines With the so- I dium to reduce the pressure by 3pounds. But the expansion of the nitrogen at the elevated valve operating temperatures causes an internal valve pressurey greatly inl excess of the ambient pressure, as shown by the fact that when 4a conventional valve operating at an elevated temperature is pierced, the sodium is blasted out. As Will be shown more clearly hereinbelow, the

`vapor pressure of metallic sodium is so lowhas to preclude any appreciable vaporization of the 'sodium in conventional valves.

Conventional sodium filled valves on the order' y dium filled*A hollow valves. l should preferably be extended to a degree Where of .those disclosed by Heron are formed with a relatively large cavity in the valve head and with a relatively constricted hollow passagethrough the stem.` The sodium must flow from the 'valve head cavity through a restricted aperture into the stem in order to transfer heat to the valve stem for dissipation therefrom. The small aperture into'the valve stem may become gas pressure locked, for the liqueed sodium has a fairly high viscosity even at elevated temperatures.

The situation presented by the conventional so-y It should `alsobe noted kthat high internal v pressures decelerate the melting of the sodiumh.

as indicated by the followingtable:

. Melting Pressure, lig/cin.2 point of l Y sodium Further', the air present in the internal cavities of conventional valves is a poor conductor of lheat'. The agitation and the high temperatures tend to cause increased adsorption of air by the sodium, thus reducing the heat transfer to' the "valve stem surface due tothe insulating chiaracteristics of the sodium-air foam generated when the valves are operated.

In brief, the air present'within conventional i sodium filled valves impedes the transfer of heat from theA valve head to the valve stem by delay` `ing liquefaction of the sodium, by forming Ia gas lock within the valve and otherwise interfering with the free movement of the sodium, and by acting as anA insulating medium, particularly in the form of an air-sodium foa d I have now found thatA the disadvantages pointed out can be eliminated by evacuating sothe sodium can be volatilized. Thus evacuated valves dissip-ate heat much more. rapidly than conventional sodium `lled valves. Aside -from the fact that the 'liquefaction of the sodium is The evacuation not delayed, that no gas locks are formed, and that no insulation is eiected by air, the efflciency of the valve is greatly enhanced by volatilization of sodium in the valve head and condensation of sodium in the valve stem, with 'consequent dissipation of the heat of vaporization. Since the valve stem can: then be kept at a relatively low temperature, the resulting greater temperature gradient between the valve head and the valve stem makes for more eiii-y cient heat transfer to the valve stem for -dissipation therefrom.

The importance of effecting as completeevac- `nation as possible is shown by the data tabu'- lated hereinbelow:

Vapor pressure Temperature, C uf sodium taining hollow poppet valves by reacting coolant in the valve with another material introduced into the valve for exhausting the space in the valve. y

A still further object of the invention is to providea method of evacuating hollow poppet valves partially filled with a coolant by reacting the coolant in the valvev with oxygen for exhausting the interior of thevalve.

A still further object of the invention isto vprovide a method of increasing the cooling capacity of coolant-containing poppet valves by ,reacting the coolant in the valves with another material. Y A still further object of the invention is to provide a method of evacuating hollow poppet valves containing coolant. material by displacing air in the valves with oxygen and by reacting the oxygen with the coolant.

A specific object of the invention is to provvide a method of evacuating hollow sodiumfilled poppet valves by displacing air in the valves with Oxygen and by reacting the oxygen j with the sodium. y n 5 v yother and further objects of the invention will be apparent to those" skilled in theartl from kmoved from the valve.

the following detailed description of the annexed sheet of drawings which, by way of preferred example, illustrates one manner of carrying out the method of this invention and compares this method with another method of evacuating a poppet valve.

On .the drawing:

Figure 1 is a diagrammatic vertical cross sectional view of an evacuated sodium-containing valve prepared according to the method of this invention.

Figure 2 is a fragmentary diagrammatic vertical cross-sectional view of a valve being evacuatecl by mechanical means.

Figure 3 is a, diagrammatic vertical cross-sectional view showing the initial stage of the process for filling a valve with sodium and oxygen in a manner according to this invention described in greater detail hereinbelow.

Figure 4 is a diagrammatic vertical crosssectional View similar to Figure 3 but showing a later stage of the method illustrated in Figure 3.

As shown on the drawing:

A valve producedY according to the method. of this invention is indicated generally in Figure 1 by the reference numeral I!) and includes a head II and a stem l2. This valve is formed with a mushroom-shaped cavity including a head cavity portion I3 and a stem cavity portion I4 intercommunicating through a. constricted aperture l5 formed in the neck of the valve. The head chamber I3 forms about 3/5 of the total internal capacity of the valve I0, with the stem cavity accounting for the remainder. The contents of the Valve cavities include at ambient temperature. from 50 to 60% sodium indicated by the reference numeral I9 with the valve at rest innen-operating condition.

The valve I0 is formed with a tapered aperture IB at its top through which the valve is lled. This aperture is closed, after iilling, with a tapered plug or pin I1.

As shown in Fig. 1, the sodium I9 is broken up into globules when the Valve is operated, due to the shaking or oscillation of the sodium effected by the movement of the valve and due to boilingv of the sodium.` The sodium vapor generated will rise inside the valve stem and will tend to be condensed on the sides of the valve stem. cavity, whenthe condensed sodium will'tend to ow downwardly, as indicated by the arrows.

The evacuated valver of Fig. 1 may be obtained by mechanical means, as illustrated in Fig. 2. For instance, a suitable amount of sodium may ist bel introduced into the valve. Then a tubular member 20 may be fitted tightly over the top of the valve, the tubular member 20 being, for instance, countersunk as at 2| to adapt the member to be seated upon and to embrace the top of the valve I 0. The member 20 is formed with an internal conduit 22 registering with and wider than the aperture I6 and lined with resilient material 23 of a thickness such that the plug I1 may be held thereby while the interior of the valve IB as well as the conduit 22 are evacuated through a conduit 24 piercing the tubular member 20 near its bottom and connected to a source of vacuum. When evacuation is completed, the plug I1 may be rammed down into the aperture I6 tov seal the valve. The tubular member 2E is then re- According to this invention evacuation kof the valve is eiected chemically by lling the valve with sodium and with oxygen and then sealing the valve. When the valve is heated, the sodium will then combine with the oxygen to form sodium oxide and to exhaust the valve to an extent determined by the purity of the oxygen. Even in a large cavity valve, the amount of sodium oxide formed would not exceed 35 milligrams. If nitrogen and other inert gases are completely excluded, the interior space in the valve can be very completely exhausted. Chemical exhaustion carried out in this manner may even be more eicient than mechanical exhaustion.

Figures 3 and 4 illustrate a specific method of lling a valve with sodium and pure oxygen. As shown in Fig. 3, a valved tube 30 connected to a source of oxygen may be inserted into the valve cavity so as to reach almost to the bottom thereof. The air in the valve cavity is then washed out with a stream of pure oxygen. Metallic sodium is then extruded into the valve cavity by v means of an internally threaded pressure gun 32 having a bent nozzle 33 and a threaded piston operated by means of a handle 34. As shown in Fig. 4, the tube 30 is raised as the level of the sodium in the valve cavity rises. A current of oxygen is kept flowing through the valve cavity as long as sodium is being introduced thereinto. When enough sodium has been introduced, the nozzle 33 iswithdrawn from the aperture I6, the tube 30 is likewise Withdrawn, and the plug l1 is rammed down into the aperture I6 to seal the same. I

When a sealed valve filled-with sodium and oxygen in the manner disclosed hereinabove is exposed to valve operating temperatures, the oxygen combines with the sodium to leavethe space above the sodium almost completely exhausted.

In the finished valve there is no oxygen present which would tend to cause corrosion. The sodium present in the valve also reduces any metal oxide evacuated coolant-containing valves wherein the mobility of the liquid coolant has been greatly enhanced and the heat dissipating capacity of the valve greatly increased. At the same time, a cool-r ant vaporization-condensation cycle has been set up to further increase the rate of heat transfer from the valve head to the valve stem.

It will, of course, be understood that various I details of the .method may be Varied throughy a.

Wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claim.

I claimv as my invention:

The method of fabricating a sodium containing poppet valve which comprises forming a poppet valve with a hollow internal space open at one end only, positioning said valve with the open end uppermost, flowing oxygen into the space through said open uppermost endto displace air from the space and flll the space with oxygen at atmospheric pressure, partially filling said space with sodium through said open end, ycontinuing v ,the flowing Vof oxygen into the space during the sodium lling operation to maintain the space free from air, closing said open end to seal the hollow internal space of the valve, and heating` the sealed valve to react all the residual oxygen with some of the sodium to produce an evacuated sodium cooled valve. l l

REX DE ORE MCDILL. 

